HIV-associated nephropathy (HIVAN) is characterized by a collapsed glomerular capillary tuft with hyperplasia and hypertrophy of podocytes. Recently generated were conditional transgenic mice (podocin/Vpr) that express one of the HIV-1 accessory genes, vpr, selectively in podocytes using podocin promoter and Tet-on system. These transgenic mice developed renal injury similar to HIVAN when treated with doxycycline for 8 to 12 wk. This study demonstrated that nephron reduction by heminephrectomy markedly enhanced phenotypic changes of podocytes and led to severe FSGS within 4 wk. Nephroticrange proteinuria was observed already at 2 wk, together with dedifferentiation and dysregulation of podocytes, indicated by decreased expression of nephrin, synaptopodin, and Wilms' tumor 1 protein and increased expression of Ki-67. The acceleration of phenotypic changes of podocytes, proteinuria, and subsequent glomerulosclerosis by heminephrectomy was almost completely inhibited by angiotensin II type 1 receptor (AT1R) blocker olmesartan. In contrast, the renoprotective effect of the calcium channel antagonist azelnidipine was minimal, although it lowered systemic BP to the same level as olmesartan, demonstrating that the inhibitory effect of AT1R blocker was independent of systemic BP. Olmesartan also reduced proteinuria and prevented glomerulosclerosis even by the delayed treatment, which was initiated after the podocyte injury appeared. These data suggest that nephron reduction exaggerates podocyte injury and subsequent glomerulosclerosis, possibly through glomerular hypertension, in the mouse model of HIVAN. AT1R blockade could be beneficial in the treatment of HIVAN by ameliorating podocyte injury by avoiding the vicious cycle of nephron reduction and glomerular hypertension.
Conditional transgenic mice that express one of the human immunodeficiency virus (HIV)-1 accessory genes, vpr, selectively in podocytes using a podocin promoter and a tetracycline-inducible system develop renal injuries similar to those of patients with HIV-associated nephropathy (HIVAN). We have shown that a heminephrectomy accelerates podocyte injury, which is alleviated by angiotensin II (ANG II) type 1 receptor blocker (ARB). The current study further explores the role of ANG II in the genesis of HIVAN in this murine model. With ANG II infusion, heavy proteinuria was observed at 1 wk after the initiation of doxycycline administration to induce vpr expression in podocytes. Severe morphological and phenotypical changes in the podocytes were observed at 2 wk, together with extensive glomerulosclerosis. Norepinephrine infusion, instead of ANG II, increased the systemic blood pressure to the same level as that achieved using ANG II. However, albuminuria and glomerular injury were modest in norepinephrine-infused mice. Treatment with an ARB, olmesartan, almost completely inhibited glomerular injury. In contrast, lowering the blood pressure with a vasodilator, hydralazine, partially decreased albuminuria but did not produce any histological changes. ANG II infusion alone without doxycycline resulted in a lower level of albuminuria and minimal histological changes. These data demonstrate that excessive ANG II accelerates vpr-induced podocyte injury in a mouse model of HIVAN.
In conclusion, fluvastatin was effective in treating experimental HIVAN. The beneficial effect of this drug might be caused, in part, by preserving nephrin expression in podocytes against angiotensin II-mediated injury.
We evaluated the intraplatelet and plasma levels of transforming growth factor beta (TGF-beta) in patients with or without renal osteodystrophy (ROD) who were undergoing hemodialysis (HD). Intraplatelet and plasma levels of TGF-beta were examined before and after HD, and compared with those from healthy controls. Patients undergoing HD had significantly higher mean intraplatelet levels of TGF-beta before and after HD than did the healthy subjects (22.7 +/- 7.8 and 29.5 +/- 15.8 vs. 18.7 +/- 7.9 ng/10(5) platelets; p < .05). The mean intraplatelet and plasma levels of TGF-beta in patients after HD were significantly increased than those before HD and in healthy subjects (p < .05). Moreover, patients with ROD showed a significantly higher mean intraplatelet and plasma levels of TGF-beta than that without ROD (p < .05). To investigate the effects of TGF-beta on ROD in HD patients, we evaluated such parameters as parathyroid hormone (PTH) and alkaline phosphatase (ALP), which reflect the lesions of ROD. The mean intraplatelet level of TGF-beta was not correlated with either para-meter. Meanwhile, no correlation was observed between the intraplatelet level of TGF-beta and the hematocrit (Hct). Similarly, no correlation was observed between the intraplatelet levels of TGF-beta and the dose of erythropoietin (EPO) administered. These findings indicate that metabolism of TGF-beta occurs during HD and overproduction of TGF-beta may play an important role in the pathogenesis of ROD.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.